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a halftone negative was made and became a magenta
printer, and from the BLUE separate a yellow printer
was prepared. The printing of these plates rendered a
copy of the original CIR, rectified and geometrically
correct.
Efforts to obtain a natural green version of the imagery
required some changes in the halftone screening proce
dures. A chromatic transposition was initiated where
the printing plates were used out of their normal
sequence. Briefly the steps included:
A. 1. The RED separate was used to prepare the
black accent halftone at a 45-degree screen
angle.
2. The RED separate was also used to prepare
the magenta halftone at a 75-degree screen
angle.
B. The GREEN separate was used to prepare the
cyan halftone at a 105-degree screen angle.
C. The BLUE separate was used to prepare the
yellow halftone at a 90-degree screen angle.
D. A unique procedure was performed at this
point to insure proper color reproduction.
The magenta halftone and the yellow half
tone are both copied, dot for dot into half
tone positive form. These two positives
were sandwiched together and contact printed
to obtain a new, combined yellow halftone.
The 75-degree-angled dots add yellow to
the magenta imagery to obtain the brown
tones. The remaining 90-degree-angled
dots perform their normal function of adding
support to the cyan color to give a green
rendition where necessary (see Figure 5)-
CHROMATIC TRANSPOSITION
COLOR REPRODUCTION
Figure 5*—Flow diagram of chromatic transposition
reproduction